Other than using the federal lands more _and_ contacting your representatives (via phone!!) to express your support for keeping public federal lands, yes, donate.

While your money probably won't be ill-spent with your run-of-the-mill environmental groups, I'd really recommend searching out right-leaning groups that support public federal lands, like the American Conservation Coalition (https://acc.eco).

Sadly, the right has—for a variety of reasons—all but abandoned environmentalism and that's been a major hurdle for those of us who want to protect the environment. Eco-right groups have a _much_ better shot at changing the opinions of right-leaning folk than progressive groups like the Sierra Club do.

Full disclosure: I'm one of ACC's 42 unpaid volunteers.